1. Field of the Invention
The invention relates to a telecommunication switching system, more particularly to a telephone system and method for permitting a user to use any telephone terminal in the same operational environment as his or her own telephone terminal by means of a virtual telephone terminal assigned to the user.
2. Description of the Prior Art
A variety of telephone features has become available with advances in exchange facilities and telephone terminals. An integrated service digital network (ISDN) provides, for example, calling number indication, call transfer, voice mail services, a private branch exchange (PBX) enables trunk calling limited by a class of service, various kinds of call transfers, speed dialing and function assignment to keys, etc. Most of these features are achieved by using personalized data stored in a feature data storage location associated with the user's home base telephone in the telephone exchange to which the user's home base telephone is connected. According, there is a problem in the prior art that the personalized features are available only from the user' home base telephone.
Arrangements have been devised so far to cope with the problem. One such arrangement is disclosed by Tadahiro Akiyama in U.S. Pat. No. 4,759,056 (1988). Also, Chinmei C. Lee et al. describes in U.S. Pat. No. 4,899,373 an arrangement for making personalized telephone features available to users away from their home base by storing data associated with their ID in a nationally accessible data base system.
However, in such arrangements, a service required by a user may not be supported for the type of the telephone terminal being used by the user. Since neither Akiyama nor Lee et al. have taken telephone terminal types into account in the above cited arrangements, the above problem will rise when the arrangements are applied to a public switched telephone network or a PBX to which various types of telephone terminals are connected.
Another problem with the prior art is that a call is not necessarily connected to the telephone terminal at the location where there is a person to whom the caller desires to talk because the call is placed by specifying as a destination the terminal number or directory number of a telephone terminal at a location where the caller expects the person to be.